PLT Scheme version 4.2 is now available from
- A new statistical profiler is now available; see the "profiler" manual for more information. Currently, the profiler supports only textual output, but future plans include a GUI interface and DrScheme integration.
- The world teachpack is now deprecated. Its replacement universe has a new interface that uses strings instead of symbols and characters.
- Web-server: Native continuations in the stateless servlet language support capturing continuations from untransformed contexts; soft state library for stateless servlets.
- DrScheme's Stepper can now jump to a selected program expression.
- New in scheme/base: hash-has-key?, hash-ref!, in-sequences, in-cycle. New in scheme: count, make-list (from scheme/list), const (from scheme/function).
- Some performance improvements, including faster start-up for small programs. The latter is a result of delaying module invocations at higher phases (compile time, meta-compile time, etc.) until compilation is demanded at the next lower phase; this on-demand instantiation is per-phase, as opposed to per-module within a phase.